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gravity-force-lab-basics_a11y_view.html
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<!DOCTYPE HTML>
<!-- Top-level HTML file for viewing, generated by 'grunt generate-a11y-view-html' DO NOT EDIT THIS FILE ONCE BUILT-->
<html>
<head>
<meta charset="utf-8"/>
<meta http-equiv="X-UA-Compatible" content="IE=edge"/>
<meta name="apple-mobile-web-app-capable" content="yes">
<meta name="phet-sim-level" content="production">
<!--have to scroll right and left! allows to resize also-->
<meta name="viewport" content="width=device-width, initial-scale=1">
<title>A11y View: Gravity Force Lab: Basics</title>
<style>
html {
font-family: Arial, Helvetica, sans-serif;
line-height: 1.4;
}
body {
margin: 1em;
background: #ccc;
}
h1, h3, p {
margin-top: .55em;
margin-bottom: 0;
padding: 0;
}
.alert_copy_container ul {
-webkit-padding-start: 1.1em
}
.left {
width: 47%;
position: -webkit-sticky;
position: sticky;
top: .55em;
display: inline-block;
}
/* This class was found online as a way to preserve an iframe aspect ratio,
see https://fettblog.eu/blog/2013/06/16/preserving-aspect-ratio-for-embedded-iframes/*/
iframe {
width: 100%;
position: fixed;
}
.aspect-ratio {
position: relative;
width: 100%;
height: 0;
padding-bottom: 69%;
}
.aspect-ratio iframe {
position: absolute;
width: 100%;
height: 100%;
left: 0;
top: 0;
}
div.right {
background: #ccc;
float: right;
width: 47%;
overflow: auto;
}
div.clearfix {
clear: both;
}
p.alert {
opacity: 0.6;
}
div.alert_copy_container {
background: #e5c45b;
border-radius: 1em;
padding: .25em .75em 1em;
min-height: 18em;
}
p.alert_copy {
min-height: 5em;
}
div.dom_copy_container {
background: #a0e1e7;
border-radius: 1em;
padding: 1em;
}
div.dom_copy_container li {
margin-bottom: .5em;
}
div.wrapper {
height: auto;
width: 97%;
}
.dynamic {
background-color: #9adaa6;
border-bottom: double .167em #000; /*or a border in dark green*/
}
div#alerts, div#pdom {
margin-bottom: 1.1em;
}
em { /* this is the same as the dynamic class, but should be changed as part of https://github.com/phetsims/a11y-research/issues/67*/
background-color: #9adaa6;
border-bottom: double .167em #000; /*or a border in dark green*/
}
.highlight {
/*use outline instead of border because border doesn't apply to all DOMElements, add margin because outline
doesn't take up any space*/
outline: thick double red;
margin: 1%;
}
.bold {
font-weight: bold;
}
.assertive {
background-color: pink; /* do not change color without changing the doc in "About Interactive Alerts" */
border-radius: .2em;
}
.activity-log-heading-container {
display: flex;
align-content: space-between;
align-items: flex-start;
justify-content: space-between;
padding-top: 0.5em;
}
.activity-log-heading-item {
align-self: center;
font-size: 1.17em;
}
/* ************SAFARI ONLY *********************** */
.left-safari {
display: inline-block;
width: 47%;
}
</style>
</head>
<body>
<div class="wrapper">
<div id="content">
<div id="intro">
<h1>A11y View: Gravity Force Lab: Basics</h1>
<details>
<summary>About the A11y View Tool</summary>
<p>
The A11y View is a design and presentation tool that visually displays a copy of the descriptions we design
for the Interactive Description feature. The State Descriptions (blue box) track the current state of the
simulation. The Responsive Descriptions (orange box) deliver relevant changes in real time as they happen.
Using this tool, designers can test and assess the descriptions during the design process without using a
screen reader. Educators can also use this tool to see if the content of the descritpions meets their teaching
and learning needs.
</p>
<p>
<b>Please note:</b> The A11y View is not for learners. In learning contexts, screen reader users access the
Interactive Desctiption feature using the same simulation as everyone else.
</p>
</details>
</div>
<!--The sim and alert containers will both be placed in here -->
<div id="left" class="left">
<div class="aspect-ratio">
<iframe id="iframe" allowfullscreen scrolling="no" title="Interact with Gravity Force Lab: Basics"></iframe>
</div>
<div id="alerts">
<div class="activity-log-heading-container">
<h3 class="activity-log-heading-item">Activity log of Responsive Descriptions</h3>
<button class="activity-log-heading-item" id="clear-activity-log-button">Clear Log</button>
</div>
<details>
<summary>About Responsive Descriptions</summary>
Responsive Descriptions are a combination of object responses, descriptions of changes made directly to
interactive objects, and context responses, descriptions of changes to the surrounding context. Together, they
are designed to deliver relevant changes in real time as they happen. The object and context responses powered
by ARIA Live appear in the activity log below. The object responses for slider interactions are powered by the
aria-valuetext attribute, and are found in grey text under slider interactions in the blue box.
</details>
<div id='alert-copy-container' class='alert_copy_container' role='presentation'>
<div id='polite-element-container'>
<ul class='alert_copy' id='alert-list'></ul>
</div>
</div>
</div>
</div>
<!--The PDOM copy will be placed in this container -->
<div class="right" id="right">
<div id="pdom">
<h3>State Descriptions for Gravity Force Lab: Basics</h3>
<details>
<summary>About State Descriptions</summary>
State Descriptions are a combination of static state descriptions (descriptions that never change) and dynamic
state descriptions (descriptions that update silently as the simulation changes). Together, they form a
complete description of the current state at any given moment. These are the descriptions that a screen reader
users can read through or review as they feel the need when they accessing a simulation (i.e., not the A11y
View tool).
</details>
<div id="dom-copy-container" class="dom_copy_container" role="presentation"></div>
</div>
</div>
<!--clear the blocks after the float effect-->
<div class="clearfix"></div>
</div>
</div>
<script type="application/javascript">
const IS_BUILT_STRING = '{{IS_BUILT}}';
const IS_BUILT = IS_BUILT_STRING.indexOf( '{{' ) !== 0; // escape for better syntax highlighting support
// Grab all query parameters to pass to the simulation, and a couple of params that are required for this test
let simulationQueryString = window.location.search;
if ( simulationQueryString.indexOf( '?' ) >= 0 ) {
simulationQueryString += '&';
}
else {
simulationQueryString += '?';
}
const noPostMessage = simulationQueryString.indexOf( 'postMessageOnLoad&postMessageOnError' ) === -1;
const noAccessibility = simulationQueryString.indexOf( 'supportsInteractiveDescription' ) === -1;
noPostMessage && ( simulationQueryString += 'postMessageOnLoad&postMessageOnError&' );
noAccessibility && ( simulationQueryString += 'supportsInteractiveDescription=true' );
// in unbuilt mode and on phet-server, the brand suffix is removed
const filenameEnding = ( window.location.hostname === 'phet.colorado.edu' || !IS_BUILT ) ? '.html' : '_phet.html';
const repoLocale = 'gravity-force-lab-basics_en';
const simURL = repoLocale + filenameEnding + simulationQueryString;
// set the source of the sim iframe
document.getElementById( 'iframe' ).setAttribute( 'src', simURL );
// apply sticky styling for all browsers except chrome.
const left = document.getElementById( 'left' );
const ua = navigator.userAgent.toLowerCase();
if ( ua.indexOf( 'safari' ) !== -1 ) {
if ( ua.indexOf( 'chrome' ) > -1 ) {
left.classList.add( 'left' );
}
else {
left.classList.add( 'left-safari' );
}
}
</script>
<script>
// Number of alerts that remain in the Activity log before fading out.
const ACTIVITY_LOG_LENGTH = 10;
/*******************************************************************************
* Helper Functions
*/
/**
* Get all 'element' nodes off the parent element, placing them in an array for easy traversal. Note that this
* includes all elements, even those that are 'hidden' or purely for structure.
*
* @param {HTMLElement} ancestor - parent whose children will be linearized
* @returns {HTMLElement[]}
*/
function getAllDOMElementsAsLinear( ancestor ) {
// gets ALL descendant children for the element
const children = ancestor.getElementsByTagName( '*' );
const linearDOM = [];
for ( let i = 0; i < children.length; i++ ) {
// searching for the HTML element nodes (NOT Scenery nodes)
if ( children[ i ].nodeType === Node.ELEMENT_NODE ) {
linearDOM[ i ] = ( children[ i ] );
}
}
return linearDOM;
}
/**
* Apply the necessary styling to the PDOM copy so that it looks and behaves well. This includes removing from
* navigation order and ensuring that all of the styling copied from the actual PDOM is removed so that the copy
* is visible and elements have proper dimensions.
*
* @param {HTMLElement} root - ancestor element, this and all descendants will be styled
*/
function styleCopy( root ) {
const allElements = getAllDOMElementsAsLinear( root );
for ( let i = 0; i < allElements.length; i++ ) {
const element = allElements[ i ];
// make sure nothing in copy is focusable
element.tabIndex = '-1';
// make sure that styling is removed, unless some styling was added just for the copy
if ( element.className !== 'pdom-style' ) {
element.removeAttribute( 'style' );
}
}
}
/**
* Convert the inline ARIA labels with label information to input values or additional label elements in the
* PDOM copy so that they are visible in demonstrations. For example, this could be an aria-label, aria-valuetext,
* and so on.
*
* @param {HTMLElement} rootNode - descendants of this root are traversed so we have
*/
function addInlineAttributesTHTML( rootNode ) {
// all elements in the PDOM - a defensive copy since we may be adding new elements to the DOM
const allElements = Array.prototype.slice.call( rootNode.getElementsByTagName( '*' ) );
for ( let i = 0; i < allElements.length; i++ ) {
const element = allElements[ i ];
// this check works because PDOMInstance sets hidden on the entire subtree of PDOMInstances when not visible on
// an accessible display rather than just the hidden ancestor
if ( !element.hidden ) {
if ( element.hasAttribute( 'aria-label' ) && element.innerHTML === '' ) {
const ariaLabel = element.getAttribute( 'aria-label' );
// remove the style
element.removeAttribute( 'style' );
if ( element.tagName.toLowerCase() === 'input' ) {
if ( element.type === 'button' ) {
// set the value of the input to be the same as the aria-label appears inside the button
element.setAttribute( 'value', ariaLabel );
}
else {
// add a special label element to appear before the input element
const labelElement = document.createElement( 'label' );
labelElement.textContent = ariaLabel;
const parentElement = element.parentNode;
parentElement.insertBefore( labelElement, parentElement.firstChild );
}
}
else {
// if not an input, then add it to the innerHTML of an element, without overriding what is already there.
element.innerHTML = ariaLabel + element.innerHTML;
}
}
if ( element.hasAttribute( 'aria-valuetext' ) ) {
// if the element has aria-valuetext, render this text in a new element so we can see the content of this
// inline attribute
const valueTextElement = document.createElement( 'p' );
valueTextElement.className = 'pdom-style';
valueTextElement.style.opacity = 0.55;
valueTextElement.textContent = element.getAttribute( 'aria-valuetext' );
// insert directly after the element that has the valuetext. This handles the case if element is last, see https://stackoverflow.com/questions/4793604/how-to-insert-an-element-after-another-element-in-javascript-without-using-a-lib
element.parentNode.insertBefore( valueTextElement, element.nextSibling );
}
}
}
}
/**
* Copy the necessary PDOM content over to the a11y view
* @param {HTMLElement} pdomRoot
* @param {HTMLElement} copyContainer - the parent of where the copy will be added in the a11y view
*/
function setPDOMCopyContent( pdomRoot, copyContainer ) {
// This is extremely inefficient every time the document changes, make a new copy, remove
// the visual DOM, and add a new one
copyContainer.innerHTML = '';
const pdomCopy = pdomRoot.cloneNode( true );
pdomCopy.removeAttribute( 'style' );
copyContainer.appendChild( pdomCopy );
addInlineAttributesTHTML( pdomCopy );
// we have to update styles of all elements when they are cloned
styleCopy( pdomCopy );
}
/**
* Add an observer to the PDOM root that will update the a11y view copy whenever the sim pdom changes.
* @param {HTMLElement} pdomRoot
* @param {HTMLElement} copyContainer - the PDOM copy will be added as a child here, see setPDOMCopyContent
* @param {Object} mutationConfig
*/
function addPDOMObserver( pdomRoot, copyContainer, mutationConfig ) {
let dirty = false;
// poll for updates to help performance on chrome
setInterval( () => {
if ( dirty ) {
// update the PDOM copy after a delay to fix a FF/Safari bug where cloneNode prevents hidden DOM elements
// in the iframe from staying hidden - see https://github.com/phetsims/chipper/issues/648
setTimeout( () => {
setPDOMCopyContent( pdomRoot, copyContainer );
dirty = false;
}, 10 );
}
}, 300 ); // as of this writing, 200 ms was pretty good, but could get a bit laggy at times on chrome while using NVDA.
// whenever an element in the parallel DOM changes, we need to update its copied element as well
const domObserver = new MutationObserver( mutations => { dirty = true; } );
// pass in the target node, as well as the observer configuration options
domObserver.observe( pdomRoot, MUTATION_OBSERVER_CONFIG );
}
/**
* add mutation observers to each of the aria-live elements
* @param {HTMLElement} originalElement
* @param {HTMLElement} listElement
* @param {Object} mutationConfig
*/
function addLiveObserver( originalElement, listElement, mutationConfig ) {
const liveObserver = new MutationObserver( mutations => {
mutations.forEach( mutation => {
// Only display added DOM nodes. ariaLiveAnnouncer will remove the content from aria-live elements so that it
// can't be read by the virtual cursor. This registers as a "mutation", but we don't want to display
// the removal.
if ( mutation.addedNodes.length > 0 ) {
const alertText = mutation.target.textContent;
// update the text content of the copied element to match the element in the iframe document
// create a list item to add to the alert list
if ( alertText.length > 0 ) {
const listItem = document.createElement( 'li' );
listItem.style.opacity = 1.0;
listItem.textContent = alertText;
if ( mutation.target.id.includes( 'assertive' ) ) {
listItem.classList.add( 'assertive' );
}
listElement.insertBefore( listItem, listElement.children[ 0 ] );
// items fade out as they get older
for ( let j = 0; j < listElement.children.length; j++ ) {
listElement.children[ j ].style.opacity = 1.0 / ( j + 1 ) + 0.50;
}
// if the list is too large, remove the last items from the list
const childrenArray = Array.prototype.slice.call( listElement.children );
const fadeArray = childrenArray.slice( ACTIVITY_LOG_LENGTH, childrenArray.length );
for ( let i = 0; i < fadeArray.length; i++ ) {
const fadeChild = fadeArray[ i ];
const intervalId = window.setInterval( () => {
fadeChild.style.opacity = fadeChild.style.opacity * 0.95;
// stop animating and remove child
if ( listElement.contains( fadeChild ) && fadeChild.style.opacity < 0.1 ) {
window.clearInterval( intervalId );
listElement.removeChild( fadeChild );
}
}, 20 );
}
}
}
} );
} );
liveObserver.observe( originalElement, mutationConfig );
}
/**
* Remove all alerts from the activity log by removing all children of the parent containing them. Solution to clear
* children from https://stackoverflow.com/questions/3955229/remove-all-child-elements-of-a-dom-node-in-javascript
*/
function clearActivityLog( listElement ) {
while ( listElement.firstChild ) {
listElement.removeChild( listElement.lastChild );
}
}
// constants
// see https://developer.mozilla.org/en-US/docs/Web/API/MutationObserverInit for details
const MUTATION_OBSERVER_CONFIG = {
attributes: true,
childList: true,
characterData: true,
subtree: true
};
// handling messages from sims
window.addEventListener( 'message', event => {
if ( !event.data ) {
return;
}
let data;
try {
data = JSON.parse( event.data );
}
catch( e ) {
return;
}
// if load is successful, create a visualization of the parallel DOM
if ( data.type === 'load' ) {
const simFrame = document.getElementById( 'iframe' );
const innerWindow = simFrame.contentWindow;
// eslint-disable-next-line dot-notation
const PDOMRoot = innerWindow[ 'phet' ].joist.display.pdomRootElement; // copy of the parallel DOM
// get the alert dom elements from the iframe's inner document
// eslint-disable-next-line dot-notation
const ariaLiveElementsContainer = innerWindow[ 'phet' ].joist.sim.display.descriptionUtteranceQueue.announcer.ariaLiveContainer;
// get the alert dom elements from the PDOM copy
const alertList = document.getElementById( 'alert-list' );
// strip the styling from the copied DOM elements
alertList.removeAttribute( 'style' );
// get the parent container for the parallel DOM copy and the alert content
const copyContainer = document.getElementById( 'dom-copy-container' );
// once for initial setup
setPDOMCopyContent( PDOMRoot, copyContainer );
// update the PDOM copy whenever the sim's PDOM changes
addPDOMObserver( PDOMRoot, copyContainer, MUTATION_OBSERVER_CONFIG );
// observe each of the live elements and add new text content to the list view
for ( let i = 0; i < ariaLiveElementsContainer.children.length; i++ ) {
addLiveObserver( ariaLiveElementsContainer.children[ i ], alertList, MUTATION_OBSERVER_CONFIG );
}
// clear all alerts when the "Clear Log" button is pressed
const clearButton = document.getElementById( 'clear-activity-log-button' );
clearButton.addEventListener( 'click', () => clearActivityLog( alertList ) );
// set focus to the loaded iframe
document.getElementById( 'iframe' ).focus();
// Provide fake focus highlighting to the PDOM copy based on what is actually highlighted in the sim.
let previousElement = null;
setInterval( () => {
if ( previousElement ) {
previousElement.classList.remove( 'highlight' );
}
previousElement = document.getElementById( 'iframe' ).contentWindow.document.activeElement;
previousElement.classList.add( 'highlight' );
}, 500 );
}
} );
</script>
</body>
</html>